Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (6,877)	$ 3,303	$ (16,883)	$ 5,867
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on investments	178	6	68	(12)
Other comprehensive income (loss), net of tax	178	6	68	(12)
Comprehensive income (loss)	$ (6,699)	$ 3,309	$ (16,815)	$ 5,855